1. Field of the Invention
The present invention relates to a semiconductor apparatus, a structure of a semiconductor device being sealed within a silicon substrate.
2. Description of the Related Art
Many types of packaging structures for semiconductor devices have been proposed, for example, some cases employ the semiconductor device with such a structure that the semiconductor device is sealed within a predetermined space. This makes a semiconductor device more stable, and more tolerant to deterioration thereof.
For example, to package MEMS (micro-electromechanical system) device as a packaged semiconductor device, a structure with having so called “cavity” is employed for accommodating the device within a predetermined space, and sealing it.
The MEMS device is generally used together with a driver device for the MEMS device. Therefore, in a semiconductor apparatus (package) using the MEMS device, both of the MEMS device and the driver device must be packaged.
FIG. 1 is an example of the structure for a semiconductor apparatus including a MEMS device. In the semiconductor apparatus shown in this figure, a MEMS part 2 and a driver 3 are mounted side by side on a substrate 1 which might be made of ceramic, for example.
The MEMS part 2 is structured so that a MEMS device 2B is accommodated inside a cavity 2A which is made of a ceramic material, the MEMS device is sealed by a lid 2C made of kovar. On the other hand, a driver device 3A is directly mounted on the substrate 1 such as disclosed in Japanese Published Unexamined Patent Application No. 2004-281530.
However, in the above-described semiconductor apparatus, since the MEMS device is sealed and packaged, while the driver device is packaged separately, it is difficult to downsize the semiconductor apparatus including the MEMS device. On top of this, as to the ceramic material forming the cavity and the substrate, this material is difficult to use for micromachining, which makes it difficult to downsize the semiconductor apparatus. This is partly because most of the ceramic package would shrink during the course of calcining due to its own property of material.
Alternatively, it is also considered to make the cavity by employing silicon, which is more suitable material for the usage of micromachining. However, a silicon wafer that is commercially available might be something in a range from 600 to 800 micrometers in thickness. In this regard, it is practically difficult to form the depth of the concave portion that is adequate for packaging the semiconductor devices as described above.
Although it would be possible to form the concave portion deeply enough for the above mentioned purpose in case of using a special thick substrate which is formed thicker than that of being generally easily to obtain, the cost for manufacturing such a semiconductor substrate would become more high, which is not realistic when considering productivity at the time of mass production.
More overly, even if one attempts to deeply form the concave portion, variation in the shape (depth and angle, etc.) of the concave portions increases, which lowers the yield (productivity) of the semiconductor apparatus to be formed.